Disk drives are digital data storage devices which allow host computer systems to store and retrieve large amounts of data in a fast and efficient manner. A typical disk drive includes one or more magnetic recording disks which are mounted to a rotatable hub of a spindle motor and rotated at a high speed. An array of read/write transducers is disposed adjacent to surfaces of the disks to transfer data between the disks and a host computer. The transducers can be radially positioned over the disks by a rotary actuator and a closed loop servo system, and can fly proximate the surfaces of the disks upon air bearings.
A plurality of nominally concentric tracks can be defined on each disk surface. A preamp and driver circuit generates write currents that are conducted through the transducer to selectively magnetize the tracks during a data write operation, and amplifies read signals generated by the transducer from the selective magnetization of the tracks during a data read operation. A read/write channel and interface circuit are connected to the preamp and driver circuit to transfer the data between the disks and the host computer.
The servo system can operate in two primary modes: seeking and track following. During a seek, a selected transducer is moved from an initial track to a target track on the corresponding disk surface. The servo system applies current to an actuator motor to first accelerate and then decelerate the transducer toward the target track.
During the seek, the servo system may repetitively measure the actual velocity of the transducer and adjust the current in relation to velocity error (i.e., the difference between the actual velocity and a target velocity). As the transducer approaches the target track, the servo system initiates a settle mode to bring the transducer to rest over the target track within a selected settle threshold, such as a percentage of the track width from track center. Thereafter, the servo system enters the track following mode wherein the transducer is nominally maintained over the center of the target track until another seek is performed.
As will be appreciated, a disk drive is primarily utilized to transfer data between the tracks of the disks and the host computer. Such data transfer operations usually cannot occur during a seek, but rather require the drive to be in track following mode. Hence, to maximize disk drive data transfer rate capabilities, disk drives can attempt to obtain minimum average seek times. However, the forces that can be exerted on the actuator to obtain minimum average seek times can cause vibration of the actuator and the disk drive, and can result in a decrease in the seek performance and undesirable acoustical noise. Moreover, vibrations from one disk drive may interfere with the operation of other disk drives mounted within the same enclosure.
In addition, the electric current applied to the actuator motor to obtain minimum seek times may result in undesirable heating of the disk drive assembly and/or elements thereof. Heating of the disk drive assembly may have a number of deleterious effects on its operation. For example, since various components of a disk drive may have different coefficients of thermal expansion, heating of the disk drive, or components thereof, may result in mechanical instability and associated errors in drive operation. Further, excessive heat may damage sensitive components of a disk drive, such as the platter surfaces, the printed circuit board assembly (PCBA) and associated components, the read/write transducer, the pre-amplifier circuit and/or other components.